The reactions. of different classes of hydrocarbons on catalysts selectively permeable with respect to hydrogen are considered. The possibilities of membrane catalysts to increase the rate and selectivity of reactions, to obtain incomplete hydrogenation products, and to decrease the competition between the adsorption of the substance hydrogenated and hydrogen are demon started. The coupling of reactions on membrane catalysts whereby it is possible to achieve a reaction, which does not occur spontaneously, as a result of the decrease of the free energy of the coupled reaction when the substance common to the two reactions passes through the membrane catalyst is discussed. © 1974 The Chemical Society and The British Library.